A clinical analyzer is an example of sample analyzer conventionally used in the field of clinical laboratory examination. Evaluation of sample quality is performed by measuring interference substances (hemoglobin, bilirubin, chyle and the like) in the sample prior to examination of target substances that are the object of examination. Interference substances are present in samples together with target substances, and may adversely affect the measurement of a target substance. These interference substances might prevent accurate optical measurement of the target substance. The concentrations of these interference substances can be determined by measuring optical absorbance at several different wavelengths specific to each interference substances. If chyle is present in a sample, it is difficult to accurately measure concentration of bilirubin or hemoglobin because the absorbance baselines at the specific wavelengths of bilirubin and hemoglobin are elevated by the chyle. It is desirable that hemoglobin and bilirubin measurements are performed so as to be uninfluenced by the presence of chyle when measuring interference substances during evaluation of sample quality.
Conventional measuring methods have been proposed for eliminating the influence by chyle by estimating an optical absorbance at a predetermined wavelength and subtracting the estimated optical absorbance from the measured optical absorbance at that wavelength by using cycle absorbance represented as an exponential function of the wavelength (for example, refer to Japanese Laid-Open Patent Publication No. 6-66808). According to the measuring method disclosed in Japanese Laid-Open Patent Publication No. 6-66808, an absorbance A at a predetermined wavelength λ is estimated by substituting the absorbance obtained at the wavelength (660 nm), which hemoglobin and bilirubin do not substantially absorb and chyle does absorb, with an exponential function (A=α·λβ (where A represents the optical absorbance, a represents a constant attributed to the particle, β represents a constant attributed to mean particle size, and λ represents a wavelength)) representing the relationship between the wavelength and the chyle absorbance.
Since only a single absorbance is used and the absorbance is at the wavelength which hemoglobin and bilirubin do not substantially absorb and chyle does absorb in the measuring method disclosed in Japanese Laid-Open Patent Publication No. 6-66808, approximate expression is used to determine the unknowns a (constant attributed to the particle) and p (constant attributed to mean particle size) in the equation for estimating the optical absorbance A at a predetermined wavelength λ (A=α·β). Therefore, it is difficult to calculate an accurate estimate value (optical absorbance), which makes it difficult to obtain an accurate measurement result that does not include the influence by chyle.
In the chromogen (interference substance) measuring method disclosed in Japanese Laid-Open Patent Publication No. 6-66808, a sample blank solution is prepared by mixing a blank reaction reagent with a sample containing suspended substances (hemoglobin, bilirubin, chyle and the like). The amount of the interference substance is measured by irradiating the sample blank fluid with light of four wavelengths that include wavelengths that chyle absorbs and hemoglobin and bilirubin does not absorbs substantially. Specifically, the amount of chyle is calculated by assuming an optical absorbance expressed as an exponential function of wavelength and determining the regression curve of the wavelength-absorbance. Furthermore, the amounts of hemoglobin and bilirubin are calculated by assuming a constant relationship established between absorbance at different wavelengths, and preparing and solving simultaneous linear equations relating to absorbance at a measured wavelength.
According to the method of Japanese Laid-Open Patent Publication No. 6-66808, a sample blank fluid that can not be used in the main measurement (measurement that is the conventional goal) must be prepared for optical measurement of interference substances. Therefore, the measurement of the interference substances must be performed separately from the main measurement. Moreover, since a sample such as serum or the like must be prepared for the sample blank fluid separately from the main measurement, the sample is disadvantageously consumed before obtaining the main measurement result.
Moreover, other arts have been proposed for measuring interference substances (hemoglobin, bilirubin, chyle and the like) in samples, wherein the quality of the sample (serum and the like) is evaluated prior to performing a main measurement (for example, biochemical analysis) (for example, refer to Japanese Laid-Open Patent Publication No. 57-59151 and U.S. Pat. No. 5,734,468).
In the method for measuring chyle, icterus, and hemolysis in serum disclosed in Japanese Laid-Open Patent Publication No. 57-59151, the serum is irradiated with four wavelengths of light, and the absorbance is measured primarily using the light of shortest wavelength in the visible range (for example, 410 nm). Then, serum that has a measured absorbance greater than a set value is determined to be abnormal due to the level of chyle, icterus, or hemolysis. Secondarily, with regard to serum that has been determined to be abnormal, the degrees of chyle, icterus, and hemolysis are determined by comparing the absorbance measured using the four wavelengths of light with several types of preset standards.
Furthermore, in the analyzer disclosed in U.S. Pat. No. 5,734,468, the absorbance of a sample within a needle tube is first measured by irradiating a serum sample aspirated to the needle tube disposed in a transparent part provided in a probe using light emitted from a light-emitting diode. Then, a serum sample that has been determined to be measurable based on this absorbance is moved to the analyzer and the main measurement is performed.
However, the interference substances in a sample are measured using a sample such as serum or the like in an original concentration prior to performing the main measurement (biochemical analysis or the like) in Japanese Laid-Open Patent Publication No. 57-59151 and U.S. Pat. No. 5,734,468. Therefore, an optical measurement structure (for example, an optical sensor or probe) for measuring the sample at an original concentration must be disadvantageously provided separately from the main measurement part.